Vokera linea 28 domestic hot water problem

[oldtimespark]

Hi to all member of this forum . Please could some one help our give guideance on a hot water problem with a Vokera Linea 28.
When any hot water tap is opened the boiler fires up and the water temp rises, when the digital temp reads 50 the boiler goes out .When the digital temp goes down to around 30 it starts up again and the on off cycle goes on until the hot tap is closed.I have run the central heating and domestic hot water at the same time and the same cycle happens i.e boiler on /boiler off.
Thanks for any replys[/b]

 

[DEEARR]

From one old time spark to another, I had a similar fault with my linea 28.
As the temperature approaches the preset, the gas valve should start to modulate down via info from thermistors. To replace the thermistors is relatively inexpensive and would be my first line of attack. There are 2 of them monitoring the temp difference between both water circuits. There is horrible possibility of a PCB. problem.

 

[scatmanjohn]

Hi to all member of this forum . Please could some one help our give guideance on a hot water problem with a Vokera Linea 28.
When any hot water tap is opened the boiler fires up and the water temp rises, when the digital temp reads 50 the boiler goes out .When the digital temp goes down to around 30 it starts up again and the on off cycle goes on until the hot tap is closed.I have run the central heating and domestic hot water at the same time and the same cycle happens i.e boiler on /boiler off.
Thanks for any replys[/b]

As soon as the boiler cuts out, quickly turn off the tap. The display will change to show the temp reading from the primary thermistor.
If its up at around 90 degrees the plate heat exchanger is the likely cause

 

[oldtimespark]

Thank you both for the quick replys will change both thermistor when I can get hold of them ,did the test procedure in post from scatmanjohn.The temp readout went up to 90. What other tests can be done to isolate fault to plate heat exchanger.If plate heat exchanger is blocked what would the temperature diffrental be on inlet and outlet pipes and what diffrential would there be on a good one.

 

[Agile]

If the plate heat exchanger is blocked then you are unlikely to need to change the NTC thermistor sensors.

You will need to clean or replace it.

The correct diagnostic method to determine if its blocked is to measure the boilers flow and return temperatures. Should be about 65/45 when its working normally. If its blocked it will be about 85/35 due to the reduced primary flow rate.

Tony

 

[oldtimespark]

I have taken temperature readings on the inlet and outlet pipe work on the plate heat exchanger with a contact k-type temperature probe and Fluke temp meter. Reading were 72ºc and 90ºc .When the thermistor arrive will try the low cost fix already fitted service kit for water flow switch and diverter valve

 

[Agile]

Do you really think the return can be 90*C if the flow is only 72*C ???

If you have got those baclwards then the plate HE is badly blocked !!! A common fault !

How do you get the "degree symbols" ?

Tony

 

[scatmanjohn]

Its the plate heat exchanger.

Forget the thermistors.

As Tony has already said it is a very common problem on this boiler.

 

[mmalone]

Its the plate heat exchanger.

Forget the thermistors.

As Tony has already said it is a very common problem on this boiler.

came across 3 recently , same problem PLATE HEAT EXCHANGER..


how easy are these to clean guys ???

 

[oldtimespark]

Is there a correct way to express the temperature readings ie inlet/outlet or is it outlet/inlet thanks for all the response to my post here how to get the degree symbol
Note You must use the numeric keypad to type the numbers and not the keyboard. Make sure that the NUM LOCK key is on if your keyboard requires it to type numbers on the numeric keypad. Keep ALT key depressed while typing 0176 on numeric keypad symbol will then appear when ALT key is released

° Symbol Character Code
ALT+0176

 

[oldtimespark]

I think I have made a big mistakeand taken the temp reading on the main heat exchanger not the domestic heat exchanger

 

[Paul Barker]

No that's what Agile meant, the domestic heat exchanger is not drawing energy from the main heat exchanger because it is working at very low percentage of what a new one would do.

On this boiler it's a relatively cheap part (relative to other boilers).

Just take the bull by the horns.

I wouldn't like to pay you to change my consumer unit by the hour.

 

[Agile]

"""I think I have made a big mistake and taken the temp reading on the main heat exchanger not the domestic heat exchanger"""

Its not that important because those will be the temperatures applied to the plate heat exchanger anyway.

It just confirms that you have the usual fault of a blocked HE.

Tony

 

[oldtimespark]

No that's what Agile meant, the domestic heat exchanger is not drawing energy from the main heat exchanger because it is working at very low percentage of what a new one would do.

On this boiler it's a relatively cheap part (relative to other boilers).

Just take the bull by the horns.

I wouldn't like to pay you to change my consumer unit by the hour.

I work as an industrial maintenace tecnician on automated machine and the last distubution board I changed in a domestic/ commercial location was a long time ago,now it only plant brakedowns and some machine installation.The faults on automated plant are are not aways just replace it and see if it works because the spare stock levels are mostly kept to a bear minimum you have to diagnose the fault then do the repair .

 

[scatmanjohn]

No that's what Agile meant, the domestic heat exchanger is not drawing energy from the main heat exchanger because it is working at very low percentage of what a new one would do.

On this boiler it's a relatively cheap part (relative to other boilers).

Just take the bull by the horns.

I wouldn't like to pay you to change my consumer unit by the hour.

I work as an industrial maintenace tecnician on automated machine and the last distubution board I changed in a domestic/ commercial location was a long time ago,now it only plant brakedowns and some machine installation.The faults on automated plant are are not aways just replace it and see if it works because the spare stock levels are mostly kept to a bear minimum you have to diagnose the fault then do the repair .

And your point is?